1. Field of Invention
The invention relates to a drive unit of a vehicle, such as an electric automobile (EV) having at least a drive motor, a hybrid car (HEV), etc., and particularly relates to a drive unit improved such that no excessive inertia caused by the existence of the drive motor is applied to a parking device under a predetermined condition when a parking operation is performed.
2. Description of Related Art
A drive unit of a so-called 2-motor split type is conventionally mounted in an automobile (registered trademark Prius) and is practically used as a hybrid drive unit. Although discussed in the context of an automobile, the drive unit can be used with other types of wheeled vehicles. In this hybrid drive unit, an output from an engine is distributed to a motor (generally called a generator) and a running output side by a planetary gear. The output torque of the planetary gear is steplessly controlled by mainly controlling the operation of the motor as the generator. Further, the torque of another motor (generally called a drive motor) is synthesized together with the planetary gear output torque as necessary and is outputted to an output shaft.
The hybrid drive unit of the 2-motor split type in practical use is mounted in the automobile as a drive unit for FF (front engine-front drive; called FF in this specification). However, it is also considered that this hybrid drive unit can be mounted to an automobile of FR (front engine-rear drive; called FR in this specification) type. FIG. 7 schematically shows the hybrid drive unit of such FR type.
As shown in FIG. 7, in the automobile 51 mounting the hybrid drive unit therein, an internal combustion engine 55, such as a gasoline engine, etc. is arranged substantially between front wheels 53, 53 at the front of a vehicle body 52 such that its crank shaft is arranged in the forward-rearward direction. Further, a hybrid drive unit 56 of a type (so-called 2-motor split type) having two motors (conceptually including the generator) is arranged behind and adjacent to the engine 55. The hybrid drive unit 56 is approximately aligned with the crank shaft in the axial direction, and a first motor (generator) 57, a planetary gear 59 for power distribution and a second motor (drive motor) 60 are sequentially arranged from the engine side toward the rear of the automobile 51.
In the hybrid drive unit 56, an input shaft 62 is connected to an output shaft 55a, comprising a backward projecting portion of the engine crank shaft, through a damper device 58. The first motor 57 is coaxially arranged on the outside diameter side of the input shaft 62. The first motor 57 is of an alternating current, permanent magnet synchronous type (AC synchronous motor), and has a stator 63 fixed to a case and a rotor 65 rotatably supported with a predetermined air gap separating the rotor 65 and the inside diameter side of the stator 63.
The planetary gear 59, for power distribution, comprises a simple planetary gear coaxially arranged on the input shaft 62. The planetary gear 59 has a carrier C connected to the input shaft 62 and supporting a plurality of planetary pinions p, a sun gear S connected to the rotor 65, and a ring gear R constituting a running output portion. The ring gear R is connected to an output shaft 66 that extends backwards on the same axial line as the input shaft 62.
The second motor 60 comprises a similar AC synchronous motor, larger in size than the motor 57, and is coaxially arranged on the output shaft 66 at its outside diameter side. The second motor 60 has a stator 67 fixed to the case and a rotor 69 rotatably supported with a predetermined air gap between the rotor 69 and the inside diameter side of the stator 67.
The output shaft 66 projects from the case and extends further rearward and is connected to a differential device 72 through a flexible coupling 70 and a propeller shaft 71 (which are not shown in detail but actually have, for example, a universal joint and a center bearing). Further, the output shaft 66 is connected through the flexible coupling 70, propeller shaft 71, and the differential device 72 to rear drive wheels 75, 75 through left and right drive shafts 73l, 73r. 
In the automobile 51, of the FR type mounting this hybrid drive unit 56 thereto, the output of the engine 55 is transmitted to the carrier C of the planetary gear 59 for power distribution through the damper device 58 and the input shaft 62. In the planetary gear 59, the engine output is distributed and transmitted from the sun gear S to the first motor (generator) 57 and is also distributed and transmitted from the ring gear 59 to the output shaft 66 for driving the automobile 51. Here, the output torque and the rotation with respect to the output shaft 66 are steplessly adjusted and outputted by controlling the operation of the first motor 57. When large torque is required at a starting time, etc., the second motor (drive motor) 60 is operated and its motor torque assists the torque of the output shaft 66, is transmitted to the propeller shaft 71 and further transmitted to the rear drive wheels 75, 75 through the differential device 72 and the left and right drive shafts 73l, 73r. In the second motor 60, electricity generated by the first motor 57 is provided as energy. When the generated electric energy is insufficient, the second motor 60 is operated by further using energy from the first motor 57 and/or the second motor 60 stored in a battery. The second motor 60 also functions as a regenerative generator at a brake operating time.
The hybrid drive unit 56 is used for the 2-motor split hybrid, and the system of a type for directly connecting the second motor (drive motor) 60 to the propeller shaft 71 of the running output side is adopted.